Traditional stereo imaging uses two cameras separated along a baseline to capture two slightly different viewpoints looking in the same direction. The stereo image pair can then be projected on a stereo display and fused by the human brain to get strong cues to scene depth.
The objective of omnistereo imaging is to provide stereo cues for up to 360 degrees around an observer. Omnistereo images can be used for navigation in a virtual environment without the need to track head orientation.
The difficulty in capturing omnistereo images is that capture cannot simply be done using two cameras side by side. Such a capture would provide maximum stereo information on the median line (perpendicular to the baseline) but not stereo information along the baseline.